Her colleague, Daria Chong, 17, said the boy landed on his right side, and there was a pool of blood beneath him.

She added that they did not hear any screams.

Some passers-by stopped to help, and one started administering CPR on him before the paramedics arrived.

Photos of the scene sent to The Straits Times and posted on social media showed a hole in the ledge beside the walkway linking the malls on Orchard Road.

"Please don't be careless, life is so fragile... at Orchard Central a few mins ago. Someone climbed over the railing and the flooring broke," said Twitter user Spliffany.

The Singapore Civil Defence Force (SCDF) was alerted to the incident at 4.05pm.

A young man was taken to Tan Tock Seng Hospital and paramedics administered cardiopulmonary resuscitation en route to the hospital, SCDF said.

Police said he died in the hospital.

"This afternoon, a member of the public vaulted the railing of the level four link bridge between Orchard Central and Orchard Gateway onto a ledge and subsequently fell to the atrium," said Ms Mavis Seow, chief executive officer of Far East Organisation's retail business group.

"He was rushed to the hospital. We are deeply concerned and are currently assisting the police with their investigations of the incident."